Fuel compositions



3,266,877 Ice Patented August 16, 1966 3,266,877 FUEL COMPOSITIONS William A. Barr, Brookside, Newark, and James L. Hall, Mount Cuba, Del., assignors to Atlas Chemical Industries, Inc., a corporation of Delaware No Drawing. Filed Sept. 8, 1958, Ser. No. 759,429 19 Claims. (Cl. 44-63) This invention relates to liquid hydrocarbon fuel compositions to which anti-static properties have been imparted and to methods of producing the same. Particularly it relates to liquid hydrocarbon fuels which have had their electrical characteristics changed by the addition of acylation products of hydroxy amines derived from hexoses.

Modern engines of the internal combustion type, such as are used in automotive vehicles and propeller driven aircraft, and jet engines, such as are used in military aircraft, make use of a wide variety of liquid hydrocarbon fuels. Many of these fuels have been found to present a serious safety hazard because of their property of forming an explosive equilibrium mixture with air at temperatures encountered under normal storage and handling conditions. Handling these fuels has, in the past, presented a considerable danger because such explosive mixtures may be readily ignited by discharges of static electricity which has been accumulated in the fuel in the course of pumping and transfer operations.

Not all fuels have volatility characteristics which ordinarily permit formation of explosive equilibrium mixtures at normal temperatures. Some fuels have such high volatility that they may not be expected to form such an explosive equilibrium mixture, except at temperatures below those normally encountered, because the vapor mixtures they form in equilibrium with air are too rich to be exploded. On the other hand, other fuels have such low volatility that, except under temperature conditions higher than those normally encountered, they may ordinarily not be expected to produce vapor mixtures which are rich enough to explode.

It should be appreciated that the above discussion is confined to equilibrium conditions. Fuels which do not normally form equilibrium explosive mixtures with air at normal temperatures may form explosive mixtures when compressed or when present with air in the form of a foam or froth. Thus, although automotive fuels do not form explosive equilibrium mixtures above F., it is possible to obtain such mixtures in refinery operations at higher temperatures. For instance, when a tankful of automotive gasoline is blended by rolling with air (i.e. air is sparged into the tank as a source of agitation) an explosive mixture can be artificially created.

In general, the fuels with which the present invention will find .its principal applicability are those having such volatility characteristics that, within a temperature range between about 20 F. and about 210 F., explosive equilibrium mixtures form in air and more particularly those which form such mixtures between about 20 F. and about 100 F.

Reid vapor pressure, which is measured at 100 F., is one common measure of volatility characteristics. Fuels suitable for use in this invention will be found included within the range of Reid vapor pressures of from about 0.1 to about pounds per square inch.

One of the fuels with which the invention is particularly applicable is JP-4 jet fuel, which is completely described in military specification MIL-F-5624 C. ]P4 fuel which is a low vapor pressure, wide-cut, gasoline type hydrocarbon, forms an equilibrium explosive mixture with air between about 10 F. and about 90 F. and has a Reid vapor pressure of from 2 to 3 pounds. Another fuel with which the invention may be employed is IP-3 jet fuel, which forms such mixtures at about 45 F. and below, and has a Reid vapor pressure between 5 and 7 pounds per square inch. The invention is also applicable to fuels which are used in internal combustion engines, as, for example, high test aviation gasoline which forms explosive mixtures at about 30 F. and below, and has a Reid vapor pressure between 5.5 and 7 pounds per square inch. It is also useful with kerosene and with ordinary automotive gasoline, which latter forms such explosive equilibrium mixtures to about 10 F. and below and has a Reid vapor pressure between 10 and 15 pounds per square inch. All of these fuels may be successfully treated in the manner described below and, when so treated, are within the scope of this invention.

When dealing with fuels, such as those discussed above, it has been found that an explosion can be triggered by the spark from a charge of static electricity such as can be built up in the fuel body in the course of pumping and filling operations. WADC Technical Report 55-266 of November 1954, entitled, Frictional Electrification Effects in Fuel Flow by Dr. F. M. Ernsberger of the Southwest Research Institute (catalogued by ASTIA as AD No. 90288) is a detailed study of the theoretical aspects of this problem. In order to minimize such dangers, many precautions are now taken such as elaborate grounding systems and the use of oversize pipe lines to minimize friction and consequent static build-up.

It has been empirically determined that there is a relationship between the electrical resistivity of liquid hydrocarbon fuels and their ability to build up a charge of static electricity such as is necessary to trigger an explosion. Fuels which have an electrical resistivity of less than about 1 10 ohm-centimeters cannot build up such a charge since the static charge created in such fuels is able, by virtue of the low resistivity thereof, to ground itself as fast as it builds up.

An object of this invention is, accordingly, the provision of liquid hydrocarbon fuel in which static electricity buildup during storage or handling is inhibited so as to minimize the possibility of accidental ignition.

An addtional object of this invention is the provision of a fuel composition which is rendered highly conductive by the use of small amounts of selected additives, which additives do not interfere with the combustion characteristics of said fuel.

The above objects of this invention, as well as additional objects, will be apparent to those skilled in the art from a consideration of the following description and examples.

Briefly stated, it has been found that the fuels of the present invention have lower electrical resistivity (i.e. greater conductivity) and are inhibited against the buildup of static electricity preferably by the addition of a small amount of compounds which are acylation derivatives of hydroxy amines derived from hexoses such as glucamine or N-a-lkyl glucamines. Other hydroxy amines derived from hexoses, which are suitable for subsequent acylation to form the additives of the invention, include amines derived from fructose, glucose, galactose, sorbose and like hexoses; mixtures of glucamines and fructamines (which can be prepared, as is known in the art, by reductive amination of invert sugar-such mixtures being referred to henceforth herein as invertamine), condensation products of the above amines with up to six mols of alkylene oxides (such as ethylene oxide, propylene oxide or mixtures thereof) per mol of amine; and mixtures of any of the above products. All of the above representative materials are intended to be encompassed by the term hydroxy amines derived from hexoses as used henceforth herein. Specific examples of such amines include N-methyl glucamine, N,N-dimethyl glucamine, N-ethyl glucamine, N-methyl fructamine, galactamine and N-butyl fructamine.

The amount of the preferred additives of the invention desirable for anti-static protection is that which is sufficient to reduce the electrical resistivity of the fuel to a value below about 1X10 ohm-centimeters. Usually an amount less than 2 wt. percent will sufiice and amounts between .005% and 1.0% by weight are preferred.

The additives employed in this invention are, as stated above, acylation products of hydroxy amines derived from hexoses and include acylation derivatives of glucamine and the N-alkyl glucamines. Details of the preparation of the N-alkyl glucamines may be found in an article by P. Karrer and E. Herkenrath, Helv. Chim. Acta, vol. 20, pages 8386 (1937), and also in an article by Mitts and Hixon, 11., Am. Chem. Soc., vol. 66, pages 483-486 (1944). Preparations of methyl, ethyl, propyl, n-butyl, isobutyl, pentyl, hexyl and cyclohexyl glucamines are disclosed in these articles.

From these basic materials two types of acylation products which are useful as additives can be prepared. The first of these are amides and amide-esters of hexityl amines, which amines contain at least one amino hydrogen atom capable of amidation. Such hexityl amines include anhydro hexityl amines. The prefix anhydro, as used in this connection, indicates that H O has been split out from among hydroxyl groupings to form an inner ether. Other suitable hexityl amines include cyclized hexityl amines which contain one amino hydrogen atom. Cyclized, as used henceforth in this connection, indicates a hexityl amine residue wherein an amino hydrogen and a hydroxyl group have been split off from the molecule in the form of water. Cyclized hexityl amines of the type suitable for forming acylation products of this first type (i.e. amides and amide-esters) may also be characterized as heterocyclic secondary amines.

Representative acylation products of the first type include amides and amide esters of: glucamine, cyclized glucamine, anhydro glucamine, fructamine, cyclized fructamine, anhydro fructamine, galactamine, cyclized galactamine, anhydro galactamine, invertamine, cyclized invertamine, anhydro invertamine, N-alkyl g-lucamines (wherein the alkyl group contains from 1 to 6 carbon atoms), N-alkyl anhydro glucamine (wherein the alkyl group contains from 1 to 6 carbon atoms), N- hydroxyethyl glucamine, N-hydroxyethyl anhydro glucamine, and similar compounds all of which contain at least one amino hydrogen before acylation and which, accordingly, form either amides or amide-esters.

Products of the second type may be broadly characterized as esters of tertiary hexityl amines. Representative amines suitable for forming such esters include N,N- dialkyl glucamines (wherein each alkyl group contains from 1 to 6 carbon atoms); N-alkyl, N-hydroxy alkyl glucamines, cyclized N-alkyl glucamines, N,N-dialkyl anhydro glucamines (wherein each alkyl group contains from 1 to 6 carbon atoms per molecule), N,N-dihydroxy ethyl glucamine, and analogous compounds derived from other hexityl amines provided always that the product which is acylated is a tertiary amine.

Acylation products of the first type may be formed by heating one mol of the aforementioned amines with one mol of fatty acid at temperatures less than about 175 C. until an amide is formed and one mol of water splits out of the reaction mass. If the reaction is carried out at a temperature of 175 C. or higher, it may be continued beyond the point where only one mol of water splits out. Such further reaction will produce anhydrization or cyclization of the polyol constituent and will result in the production of further quantities of water. Preferred products for use in accordance with the present invention are anhydroamides produced when the reaction is conducted at these higher temperatures for a length of time sufficient to split out two mols of water per mol of fatty acid. Reaction with additional fatty acid will result in the production of amide-esters.

4 The production of suitable compounds is disclosed in Patent No. 1,985,424 of December 25, 1934, and Patent No. 2,703,798 of March 8, 1955.

Examples of the preparation of some typical amide products of the first type which are suitable for use as additives in hydrocarbon fuel follow:

Example I-A 1,410 grams of oleic acid were added to 990 grams of N-methyl glucamine. To reduce foaming 82.5 grams of the product of a previous batch were added to the reaction mixture. The mixture was heated for 1 hours at temperatures up to 195 C., during which time 157 cc. of water were evolved and collected from the reaction mass. The resulting product, an oleic amide of anhydro methyl glucamine, had an acid number of 6.2, a saponification number of 29 and a hydroxyl number of 400.

Example I-B 286 grams of stearic acid were added to 200 grams of N-methyl glucamine. The reactants were heated to C. and held between 180 and C. for three hours. During that time 34.5 ml. of water were evolved and collected from the reaction mass. The resulting product, a stearic amide of anhydro methyl glucamine, had an acid number of 3.7, a saponification number of 27.7 and a hydroxyl number of 411.

Example I-C 70 g. of crystalline N-methyl invertamine was reacted with 201 g. oleic acid at 185-234 C. for 3 /3 hours during which time 21 cc. of aqueous distillate was collected. The product was a viscous dark liquid, acid No. 5.8, sap. No. 96.1, OH No. 144, and 1.95% N. The product is an ester-amide of anhydro N-methyl invertamine.

Example l-D 74 g. of N-methy'l invertamine was reacted with 76 g. =lauric acid at 17l192 C. for three hours during which time 13.5 cc. of aqeous distillate was collected. The product was a brown pasty water soluble material, acid No. 10, sap. No. 31. The product is a cyclized anhydroamide.

Aliphatic monocarboxylic acids which may be used for the amidation are those having from 12 to 26 carbon atoms per molecule and include among others oleic, erucic, stearic, lauric, tridecanoic, myristic, pentadecanoic, palmitic, margaric, non-adecanoic, arachidic, behenic, cerotic, palmitoleic, elaidic, linoleic, linolenic, aliphatic acids derived from petroleum by oxidation, tallow fatty acids, mixtures of the above acids, and dimers thereof. The term aliphatic monocarboxylic acid, as used henceforth, is intended to include all of the above acids.

In the course of the amidation some simultaneous esterification may occur. The amount of esterification which occurs relative to 'amidation depends upon a number of factors such as the time and temperature of reaction and the mole ratios of fatty acid to glucamine. In general, higher temperatures and prolonged reaction times favor amidation. Presence of excess acid, of course, favors esterification. Formation of ester-amides, as distinguished from amides, however, does not interfere with the utilization of these compounds as fuel additives.

Of considerable importance in the synthesis of compounds of this first type is the maintenance of a proper ratio between hydrophilic and hydrophobic (or lipophilic) constituents. As is well known in the art, hydroxyl groups such as are present in a polyol residue give mole cules hydrophilic characteristics whereas alkyl and fatty acid residues contribute hydrophobic characteristics. Hydrophilic characteristics can also be added by condensation with alkylene oxides or' mixtures thereof. In order to maintain a proper hydrophile-hydrophobe balance in the compounds of the invention, it has been found desirable that the sum of the carbon atoms in the alkyl group which is attached to the nitrogen atom and the carbon atoms derived from the fatty acid total at least 15. Thus, for example, when lauric acid is used for amidation, the alkyl group attached to the nitrogen atom must contain at least 3 carbon atoms.

Additives of the first type discussed above may be represented as amides having the following formulas or as esters of such amides:

is the acyl radical of an aliphatic monocarboxylic acid which contains from 12 to 26 carbon atoms per molecule; provided, however, that the carbon atoms in R plus those in the acyl radical total at least 15.

Products responding to the above generic formulae also include the cyclized acylation products of glucamines (as distinguished from N-alky-l glucamines) which would give compounds having structures of which the following are representative.

As stated above, the second type of acylation products may be broadly characterized as esters of tertiary hexityl amines. Illustrative of these products are the following, which are derived from an N-alkyl glucamine and which may be referred to as mono fatty acid esters of cyclized N-methyl glucamine:

These compounds are made by first cyclizing an N- alkyl glucamine and thereafter reacting the product with a fatty acid at temperatures above about 180 C. The acids which may be used for esterification are the same as those which are suggested above for amidation of the compounds of the first type and the same hydrophilehydrophobe considerations also apply.

These products may also be made by reacting a primary amine such as glucamine for instance, with one mol of an alkylene oxide to form a secondary amine, such as for instance N-hydroxy ethyl glucamine. Such secondary amines may then be cyclized to form a tertiary amine and thereafter acylated to form an ester.

Alternatively a primary amine may be reacted with two mols of alkylene oxide to form a tertiary amine. Thereafter, the tertiary amine may be acylated to form an ester.

Examples of the preparation of some esters of tertiary hexityl amines are the following:

Example Il-A 390 grams (2 mols) of N-methyl glucamine were heated, with stirring, under a nitrogen atmosphere at from 196 C. for 7% hours during which time 36 /2 cc. (2 mols) of H 0 were evolved. 176 grams of dark product were removed. To the balance (1 mol) of the product were added 282 grams (1 mol) of oleic acid. These reactants were heated together at 180- 208 C. for 3 hours, during which time 24 /2 cc. H O were evolved. The final product was an oleic acid ester of cyclized N-methyl glucamine.

Example II-B Example Il-C Example 111 Percent by weight JP4 jet fuel 99.975 Product of Example II-A .025

The above formulation has a resistivity of 1 10 ohmcentimeters. When the fuel was continuously pumped through a closed loop no static build-up could be detected.

Example IV Percent by weight JP-4 jet fuel 99.00 Product of Example IA 1.00

The above formulation had a resistivity of 2.9)(10 ohm-centimeters. When the fuel was continuously pumped through a closed loop, no static build-up could Other suitable formulations include the following:

Example V Percent by weight JP3 jet fuel 99.995 Lauric acid amide of N-pentyl glucamine .005

Example VI Non-leaded automotive gasoline 99.5 Tallow fatty acid amide of N-ethyl glucamine 0.5

Example VII JP-4 jet fuel 99.95 Product of Example I-B .05

Example VIII JP-3 jet fuel 99.0 Product of Example I-C 1.0

Example IX Non-leaded automotive gasoline 99.9 Product of Example ID 0.1

Example X JP4 jet fuel 99.99 Product of Example II-B .01

Example XI Kerosene 99.995 Product of Example II-C .005

Example XII Hexane 98.2 Linoleic acid amide of cyclized invertamine 0.8

One of the important tests made on these and other hydrocarbon formulations was that of electrical resistivity. In each instance the desired value of resistivity, namely below about 1 10 ohm-centimeters, was achieved when the amount of additive used was within the range of from .005 to 1.0 percent by weight.

Some data, which are representative of tests made with JP-4 jet fuel are tabulated below:

Having described our invention, what is claimed is:

1. A fuel having a resistivity of less than about 1X ohm-centimeters comprising a liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about pounds per square inch, and from 0.0005 to 2.0 weight percent of an anti-static additive selected from the group consisting of an amide of a C to C aliphatic monocarboxylic acid and a primary hydroxy hexityl amine, an amide-ester of a C to C aliphatic monocarboxylic acid and a primary hydroxy hexityl amine, an amide of a C to C aliphatic monocarboxylic acid and a secondary hydroxy hexityl amine, an amide-ester of a C to C aliphatic monocarboxylic acid and a secondary hydroxy hexityl amine, and an ester of a C to C aliphatic monocarboxylic acid and a tertiary hydroxy hexityl amine. A.

2. The fuel composition of claim 1 in which the secondary hydroxy hexityl amine is a cyclized hexityl amine.

3. The fuel composition of claim 1 in which the secondary hydroxy hexityl amine is an anhydro hexityl amine.

4. The fuel composition of claim 1 in which the tertiary hydroxy hexityl amine is a cyclized hexityl amine.

5. The fuel composition of claim 1 in which the tertiary hydroxy hexityl amine is an anhydro hexityl amine.

6. The fuel of claim 1 wherein the hydroxy hexityl amine is derived from fructose.

7. The fuel of claim. 1 wherein said hydroxy hexityl amine is derived from glucose.

8. The fuel of claim 1 wherein said hydroxy hexityl amine is derived from galactose.

9. The fuel of claim 1 wherein amine is derived from sorbose.

10. The fuel of claim 1 wherein amine is derived from invert sugar.

11. A fuel having a resistivity of less than about 1 10 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and as an antistatic additive, from 0.005 to 1.0 weight percent of an acylation product selected from the group consisting of amides and esters, of a C to C aliphatic carboxylic acid and glucamine.

12. A fuel having a resistivity of less than about 1 l0 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and, as an antistatic additive, from 0.005 to 1.0 weight percent of an acylation product selected from the group consisting of amides and esters of a C to C aliphatic carboxylic acid and an N-alkyl glucamine wherein said alkyl group contains from 1 to 6 carbon atoms, and wherein further, the total of the carbon atoms in said alkyl group plus the carbon atoms in said acid is at least 15.

13. The fuel of claim 12 wherein said acid is oleic acid and said alkyl group is methyl.

14. A fuel having a resistivity of less than about 1 10 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and, as an antistatic additive, from .005 to 1.0 weight percent of an acylation product selected from the group consisting of amides and esters of a C to C aliphatic carboxylic acid and an N-alkyl anhydro glucamine wherein said alkyl group contains from 1 to 6 carbon atoms and wherein further, the total of the carbon atoms in said alkyl group plus the carbon atoms in said acid is at least 15.

15. The fuel of claim 14 wherein said acid is oleic acid and said alkyl group is methyl.

16. A fuel having a resistivity of less than about 1 l0 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and, as an antistatic additive, from 0.005 to 2.0 weight percent of an acylation product selected from the group consisting of said hydroxy hexityl said hydroxy hexityl amides and esters of a C to C aliphatic monocarboxylic acid and a primary hexityl amine; the amount of said additive being sufficient to impart said resistivity characteristics to said fuel.

17. The fuel composition of claim 16 in which said primary hexityl amine is a primary anhydro hexityl amine.

18. A fuel having a resistivity of less than about 1X10 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between --20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and, as an antistatic additive, from 0.005 to 2.0 weight percent of an acylation product selected from the group consisting of amides and esters of a C to C aliphatic monocarboxylic acid and a secondary N-alkyl hexityl amine wherein said alkyl group contains from 1 to 6 carbon atoms; the amount of said acylation additive being sufiicient to impart said resistivity characteristics to said fuel.

19. A fuel having a resistivity of less than about 1 10 ohm-centimeters comprising liquid hydrocarbon which forms an equilibrium explosive mixture with air at a temperature between 20 F. and 210 F., said hydrocarbon having a Reid vapor pressure from about 0.1 to about 15 pounds per square inch and, as an antistatic additive, from 0.005 to 2.0 weight percent of an acylation product selected from the group consisting of amides and esters of a C to C aliphatic monocarboxylic acid and a secondary N-alkyl anhydro hexityl amine wherein said alkyl group contains from 1 to 6 carbon atoms; the amount of said additive being sufiicient to impart said resistivity characteristics to said fuel.

References Cited by the Examiner UNITED STATES PATENTS 1,985,424 12/1934 Piggott 260-211 2,638,449 5/1953 White et a1. 44-66 2,703,798 3/1955 Schwartz 260-211 2,790,779 4/ 1957 Spivack et al 44-66 X 2,951,751 9/ 1960 McDermott 44-66 FOREIGN PATENTS 749,898 6/ 1956 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

25 A. D. AKERS, W. I. ANDRESS,

Y. M. HARRIS, Assistant Examiners. 

1. A FUEL HAVING A RESISTIVITY OF LESS THAN ABOUT 1X10" OHM-CENTIMERTERS COMPRISING A LIQUID HYDROCARBON WHICH FORMS AN EQUILIBRIUM EXPLOSIVE MIXTURE WITH AIR AT A TEMPERATURE BETWEEN -20*F. AND 210*F., SAID HYDROCARBON HAVING A REID VAPOR PRESSURE FROM ABOUT 0.1 TO ABOUT 15 POUNDS PER SPUARE INCH, AND FROM 0.0005 TO 2.0 WEIGH PERCENT OF AN ANTI-STATIC ADDITIVE SELECTED FROM THE GROUP CONSISTING OF AN AMIDE OF A C12 TO C 26 ALIPHATIC MONOCARBOXYLIC ACID AND A PRIMARY HYDROXY HEXITY1 AMINE, AN AMIDE-ESTER OF A C12 TO C26 ALIPHATIC MONOCARBOXYLIC ACID AND A PRIMARY HYDROXY HEXITYL AMINE AN AMIDE OF A C12 TO C26 ALIPHATIC MONOCARBOXYLIC ACID AND A SECONDARY HYDROXY HEXITYL AMINE, AN AMIDE-ESTER OF A C12 TO C26 ALIPHATIC MONOCARBOXYLIC ACID AND A SECONDARY HYDROXY HEXITYL AMINE, AND AN ESTER OF A C12 TO C26 ALIPHATIC MONOCARBOXYLIC ACID AND A TERITARY HYDROXY HEXITY AMINE.
 2. THE FUEL COMPOSITION OF CLAIM 1 IN WHICH THE SECONDARY HYDROXY HEXITY AMINE IS A CYCLIZED HEXITY AMINE. 